I am a decent metal vocalist. I have taught all kinds of people to do deep guttural growls, from children to adults male and female.

Without creating a wall of text that will only confuse you... Two words: Exasperated sigh.

Sigh like you just died on the final boss and realized you never quicksaved.

Sigh like your dad just made the most anguishingly bad pun you've ever heard. There needs to be some disgust in this sigh.

Kind of say "uhhh" and "eww" and "ugh" at the same time.

The goal is to push air hard and leave the throat muscles loose. This will make your throat flap about and distort the sound coming out.

Okay we're getting toward wall of text, but, have you ever had a cough for a long time? And your cough got nasty sounding, even after you were all better? You trained your muscles to relax, thats why it sounds different, and you did it to help push mucous out. Screaming is pretty much the same. Once you're comfortable with all this, give it a nice loud: "Ahhhhhhhhhh!" But relax your throat as you push more air/push harder. That's where the distortion comes from.

Edit: check out extreme vocal institute for more tips. That guy explains this stuff brilliantly, and he gets into very detailed specifics.

If you're talking about the metal music kind of screaming look up "vocal fry" or "fry screaming" on YouTube. It's a technique, and it's surprisingly not that loud. Like you wouldn't use a fry scream to shout at your friend a block away but on a recording or through the mic on stage you can't tell so it looks and sounds like the singer is screaming their lungs out.

Also if you try it yourself make sure to stop before it hurts! If done correctly you can fry scream all day. If done incorrectly and ignoring the warnings signs you could end up needing surgery on your larynx. Have fun!

The kind of scream you might do in fear or anger doesn't work exactly the same as when it's done in a controlled way.

The answers already present cover how to scream as a vocal technique way better than I could (I can only growl, I've never managed to get a proper metal scream). But the kind of scream that you make involuntarily tends to be made by the vocal cords being stretched tight. You can't scream like that in a sustained way without it hurting. Too much air pressure being pushed through very taut cords, it just isn't healthy. It's also more of a head/throat generated sound and will be higher pitched.

If you want some awesome insight into the various vocal techniques used in metal, there's a YouTube channel called "the charismatic voice". The lady that does the channel is an opera singer that has turned into a metal fan, and is now doing research with a university. They recently did some amazing work with the vocalist Will Ramos, from lorna shore. MRIs, electric readings, cameras, etc. They're building a body of research into "harsh" vocals.

But the channel as a whole, she's watching/listening to videos of music, with it leaning heavily into metal. She talks about the mechanics of how the vocalists do it, and she goes in depth.

With that said, what you were doing, trying to yell for your friend to get their attention, that's more projecting your voice. When you pull the air in deep, and push from the stomach up, using your body to support that push, you can be very loud with zero distortion. Volume of the voice is all about moving air efficiently. Ever see a movie or show with a drill sergeant barking orders across a big group of soldiers? That's projection. It's the same basic techniques that opera singers and stage actors use. It's all about the air and the way you use the diaphragm with your entire body.

Anyway, some links

The channel I mentioned

The footage with the research

Some loud vocalizations that aren't distorted but are musical

A quickie tutorial on the basic technique of growling

And one for the fry scream

That growl technique is essentially the same as the way I learned to growl (though I'm not very good at it), and it matches one another user described in text.

But, no bullshit, if you're projecting your voice that clearly a block away, that's fucking legit power. I can't sing for shit, just can't hold notes steady enough to be enjoyed by other people. But I tried. Getting to the point of being able to project my speaking voice clearly over a distance took months of work. So, if you can do that, you can absolutely learn to metal scream/growl, and likely be good at it.

Personally, I scream for icecream.

I try not to.

The last time I did, it was around 3 in the morning and I just won my first chicken dinner in PUBG (when it was still new) and screamed

FUCK YEAH! SUCK MY NUTS!

Which woke up the whole house.

Look up metal screams / growls. You need to use a different part of your throat for that and there's training methods to teach you how. Obviously in those cases you'd mostly exclusively use them false vocal cords while when screaming you'd use them and your regular vocal folds for a mixed voice. There's other ways to add vocal fry but they're fairly unhealthy and can cause damage, which is why people often lose their voice when screaming too much.

Honestly OP, it sounds like what you're doing is dramatically more interesting. Can we get an example?

I use the false cord technique to do metal vocals (vocal fry was harder to learn and didn't click with me), I basically just watched different YouTube tutorials on how to do it until I watched one by Kardavox Academy on YouTube and he likened the feeling of engaging the false cords to sighing exasperatedly, and also going "ruff" very lowly like a dog.

This explanation alone is terrible, but understanding what he meant and mimicing those sounds allowed me to understand what it feels like when I engage the false cords and now I have enough control to engage or disengage it on a word by word basis or slide into it from a clean voice. It's definitely as people say, with the right technique it won't hurt, it can be tough on your voice even when done correctly, but you should never have to stop and cough, that's when you're really doing it wrong.

Get OP some singing lessons stat!

You have to stop projecting the sound from the diaphragm and move it to the throat. Essentially the opposite from singing instructions. It is obviously really bad for the vocal cords.